Internet of Things refers to a network of interaction between a person and a thing and between things by means of information transmission, synchronization, and processing over a network after information about a physical world is obtained by deploying various devices with capabilities of perception, calculation, execution, and communication. To research how to carry an Internet of Things application in a mobile communications network, the 3rd Generation Partnership Project (3GPP) proposes a machine-to-machine (M2M) communications technology and researches enhancement or optimization that is performed on the mobile communications network due to introduction of a machine type communication (MTC) device. For machine type communication, for example, an electricity meter, a water meter, and the like may be generally arranged in a place such as a building and a basement. Generally, a path transmission loss of a radio signal is relatively large in these places. To ensure normal communication of a device in such a scenario, a coverage enhancement technology is introduced to achieve an enhanced coverage objective.
Compared with a normal single transmission mode (in which no repeated sending is performed), an enhancement mode is a signal transmission mode in which a same signal or same content is retransmitted for multiple times. In a contention-based random access procedure, different machine type communication requires different repetition times. For example, to ensure reliability of a signal transmitted on each channel during random access, some machine type communication requires only 30 repetition times, some machine type communication requires 60 repetition times, some machine type communication requires 120 repetition times, and the like. Generally, the enhancement mode is divided into three levels, the coverage enhancement levels correspond to different repetition times, and for different machine type communication, different coverage enhancement levels may be selected. Likewise, repetition times required by different channels may also be different. For example, for same machine type communication, a physical downlink control channel (PDCCH) requires 30 repetition times, a physical downlink shared channel (PDSCH) may require 50 repetition times, and the like.
In the prior art, a terminal always uses one signal transmission mode, and signal transmission reliability is poor.